smalloc.c

/*
 * simple memory allocator, backed by mmap() so that it hands out memory
 * that can be shared across processes and threads
 */
#include <sys/mman.h>
#include <assert.h>
#include <string.h>

#include "fio.h"
#include "fio_sem.h"
#include "os/os.h"
#include "smalloc.h"
#include "log.h"

#define SMALLOC_REDZONE		/* define to detect memory corruption */

#define SMALLOC_BPB	32	/* block size, bytes-per-bit in bitmap */
#define SMALLOC_BPI	(sizeof(unsigned int) * 8)
#define SMALLOC_BPL	(SMALLOC_BPB * SMALLOC_BPI)

#define INITIAL_SIZE	16*1024*1024	/* new pool size */
#define INITIAL_POOLS	8		/* maximum number of pools to setup */

#define MAX_POOLS	16

#define SMALLOC_PRE_RED		0xdeadbeefU
#define SMALLOC_POST_RED	0x5aa55aa5U

unsigned int smalloc_pool_size = INITIAL_SIZE;
#ifdef SMALLOC_REDZONE
static const int int_mask = sizeof(int) - 1;
#endif

struct pool {
	struct fio_sem *lock;			/* protects this pool */
	void *map;				/* map of blocks */
	unsigned int *bitmap;			/* blocks free/busy map */
	size_t free_blocks;		/* free blocks */
	size_t nr_blocks;			/* total blocks */
	size_t next_non_full;
	size_t mmap_size;
};

struct block_hdr {
	size_t size;
#ifdef SMALLOC_REDZONE
	unsigned int prered;
#endif
};

/*
 * This suppresses the voluminous potential bitmap printout when
 * smalloc encounters an OOM error
 */
static const bool enable_smalloc_debug = false;

static struct pool *mp;
static unsigned int nr_pools;
static unsigned int last_pool;

static inline int ptr_valid(struct pool *pool, void *ptr)
{
	unsigned int pool_size = pool->nr_blocks * SMALLOC_BPL;

	return (ptr >= pool->map) && (ptr < pool->map + pool_size);
}

static inline size_t size_to_blocks(size_t size)
{
	return (size + SMALLOC_BPB - 1) / SMALLOC_BPB;
}

static int blocks_iter(struct pool *pool, unsigned int pool_idx,
		       unsigned int idx, size_t nr_blocks,
		       int (*func)(unsigned int *map, unsigned int mask))
{

	while (nr_blocks) {
		unsigned int this_blocks, mask;
		unsigned int *map;

		if (pool_idx >= pool->nr_blocks)
			return 0;

		map = &pool->bitmap[pool_idx];

		this_blocks = nr_blocks;
		if (this_blocks + idx > SMALLOC_BPI) {
			this_blocks = SMALLOC_BPI - idx;
			idx = SMALLOC_BPI - this_blocks;
		}

		if (this_blocks == SMALLOC_BPI)
			mask = -1U;
		else
			mask = ((1U << this_blocks) - 1) << idx;

		if (!func(map, mask))
			return 0;

		nr_blocks -= this_blocks;
		idx = 0;
		pool_idx++;
	}

	return 1;
}

static int mask_cmp(unsigned int *map, unsigned int mask)
{
	return !(*map & mask);
}

static int mask_clear(unsigned int *map, unsigned int mask)
{
	assert((*map & mask) == mask);
	*map &= ~mask;
	return 1;
}

static int mask_set(unsigned int *map, unsigned int mask)
{
	assert(!(*map & mask));
	*map |= mask;
	return 1;
}

static int blocks_free(struct pool *pool, unsigned int pool_idx,
		       unsigned int idx, size_t nr_blocks)
{
	return blocks_iter(pool, pool_idx, idx, nr_blocks, mask_cmp);
}

static void set_blocks(struct pool *pool, unsigned int pool_idx,
		       unsigned int idx, size_t nr_blocks)
{
	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_set);
}

static void clear_blocks(struct pool *pool, unsigned int pool_idx,
			 unsigned int idx, size_t nr_blocks)
{
	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_clear);
}

static int find_next_zero(int word, int start)
{
	assert(word != -1U);
	word >>= start;
	return ffz(word) + start;
}

static bool add_pool(struct pool *pool, unsigned int alloc_size)
{
	int bitmap_blocks;
	int mmap_flags;
	void *ptr;

	if (nr_pools == MAX_POOLS)
		return false;

#ifdef SMALLOC_REDZONE
	alloc_size += sizeof(unsigned int);
#endif
	alloc_size += sizeof(struct block_hdr);
	if (alloc_size < INITIAL_SIZE)
		alloc_size = INITIAL_SIZE;

	/* round up to nearest full number of blocks */
	alloc_size = (alloc_size + SMALLOC_BPL - 1) & ~(SMALLOC_BPL - 1);
	bitmap_blocks = alloc_size / SMALLOC_BPL;
	alloc_size += bitmap_blocks * sizeof(unsigned int);
	pool->mmap_size = alloc_size;

	pool->nr_blocks = bitmap_blocks;
	pool->free_blocks = bitmap_blocks * SMALLOC_BPI;

	mmap_flags = OS_MAP_ANON;
#ifdef CONFIG_ESX
	mmap_flags |= MAP_PRIVATE;
#else
	mmap_flags |= MAP_SHARED;
#endif
	ptr = mmap(NULL, alloc_size, PROT_READ|PROT_WRITE, mmap_flags, -1, 0);

	if (ptr == MAP_FAILED)
		goto out_fail;

	pool->map = ptr;
	pool->bitmap = (unsigned int *)((char *) ptr + (pool->nr_blocks * SMALLOC_BPL));
	memset(pool->bitmap, 0, bitmap_blocks * sizeof(unsigned int));

	pool->lock = fio_sem_init(FIO_SEM_UNLOCKED);
	if (!pool->lock)
		goto out_fail;

	nr_pools++;
	return true;
out_fail:
	log_err("smalloc: failed adding pool\n");
	if (pool->map)
		munmap(pool->map, pool->mmap_size);
	return false;
}

void sinit(void)
{
	bool ret;
	int i;

	/*
	 * sinit() can be called more than once if alloc-size is
	 * set. But we want to allocate space for the struct pool
	 * instances only once.
	 */
	if (!mp) {
		mp = (struct pool *) mmap(NULL,
			MAX_POOLS * sizeof(struct pool),
			PROT_READ | PROT_WRITE,
			OS_MAP_ANON | MAP_SHARED, -1, 0);

		assert(mp != MAP_FAILED);
	}

	for (i = 0; i < INITIAL_POOLS; i++) {
		ret = add_pool(&mp[nr_pools], smalloc_pool_size);
		if (!ret)
			break;
	}

	/*
	 * If we added at least one pool, we should be OK for most
	 * cases.
	 */
	assert(i);
}

static void cleanup_pool(struct pool *pool)
{
	/*
	 * This will also remove the temporary file we used as a backing
	 * store, it was already unlinked
	 */
	munmap(pool->map, pool->mmap_size);

	if (pool->lock)
		fio_sem_remove(pool->lock);
}

void scleanup(void)
{
	unsigned int i;

	for (i = 0; i < nr_pools; i++)
		cleanup_pool(&mp[i]);

	munmap(mp, MAX_POOLS * sizeof(struct pool));
}

#ifdef SMALLOC_REDZONE
static void *postred_ptr(struct block_hdr *hdr)
{
	uintptr_t ptr;

	ptr = (uintptr_t) hdr + hdr->size - sizeof(unsigned int);
	ptr = (uintptr_t) PTR_ALIGN(ptr, int_mask);

	return (void *) ptr;
}

static void fill_redzone(struct block_hdr *hdr)
{
	unsigned int *postred = postred_ptr(hdr);

	hdr->prered = SMALLOC_PRE_RED;
	*postred = SMALLOC_POST_RED;
}

static void sfree_check_redzone(struct block_hdr *hdr)
{
	unsigned int *postred = postred_ptr(hdr);

	if (hdr->prered != SMALLOC_PRE_RED) {
		log_err("smalloc pre redzone destroyed!\n"
			" ptr=%p, prered=%x, expected %x\n",
				hdr+1, hdr->prered, SMALLOC_PRE_RED);
		assert(0);
	}
	if (*postred != SMALLOC_POST_RED) {
		log_err("smalloc post redzone destroyed!\n"
			"  ptr=%p, postred=%x, expected %x\n",
				hdr+1, *postred, SMALLOC_POST_RED);
		assert(0);
	}
}
#else
static void fill_redzone(struct block_hdr *hdr)
{
}

static void sfree_check_redzone(struct block_hdr *hdr)
{
}
#endif

static void sfree_pool(struct pool *pool, void *ptr)
{
	struct block_hdr *hdr;
	unsigned int i, idx;
	unsigned long offset;

	if (!ptr)
		return;

	ptr -= sizeof(*hdr);
	hdr = ptr;

	assert(ptr_valid(pool, ptr));

	sfree_check_redzone(hdr);

	offset = ptr - pool->map;
	i = offset / SMALLOC_BPL;
	idx = (offset % SMALLOC_BPL) / SMALLOC_BPB;

	fio_sem_down(pool->lock);
	clear_blocks(pool, i, idx, size_to_blocks(hdr->size));
	if (i < pool->next_non_full)
		pool->next_non_full = i;
	pool->free_blocks += size_to_blocks(hdr->size);
	fio_sem_up(pool->lock);
}

void sfree(void *ptr)
{
	struct pool *pool = NULL;
	unsigned int i;

	if (!ptr)
		return;

	for (i = 0; i < nr_pools; i++) {
		if (ptr_valid(&mp[i], ptr)) {
			pool = &mp[i];
			break;
		}
	}

	if (pool) {
		sfree_pool(pool, ptr);
		return;
	}

	log_err("smalloc: ptr %p not from smalloc pool\n", ptr);
}

static unsigned int find_best_index(struct pool *pool)
{
	unsigned int i;

	assert(pool->free_blocks);

	for (i = pool->next_non_full; pool->bitmap[i] == -1U; i++) {
		if (i == pool->nr_blocks - 1) {
			unsigned int j;

			for (j = 0; j < pool->nr_blocks; j++)
				if (pool->bitmap[j] != -1U)
					return j;
		}
	}

	return i;
}

static void *__smalloc_pool(struct pool *pool, size_t size)
{
	size_t nr_blocks;
	unsigned int i;
	unsigned int offset;
	unsigned int last_idx;
	void *ret = NULL;

	fio_sem_down(pool->lock);

	nr_blocks = size_to_blocks(size);
	if (nr_blocks > pool->free_blocks)
		goto fail;

	pool->next_non_full = find_best_index(pool);

	last_idx = 0;
	offset = -1U;
	i = pool->next_non_full;
	while (i < pool->nr_blocks) {
		unsigned int idx;

		if (pool->bitmap[i] == -1U) {
			i++;
			last_idx = 0;
			continue;
		}

		idx = find_next_zero(pool->bitmap[i], last_idx);
		if (!blocks_free(pool, i, idx, nr_blocks)) {
			idx += nr_blocks;
			if (idx < SMALLOC_BPI)
				last_idx = idx;
			else {
				last_idx = 0;
				while (idx >= SMALLOC_BPI) {
					i++;
					idx -= SMALLOC_BPI;
				}
			}
			continue;
		}
		set_blocks(pool, i, idx, nr_blocks);
		offset = i * SMALLOC_BPL + idx * SMALLOC_BPB;
		break;
	}

	if (i < pool->nr_blocks) {
		pool->free_blocks -= nr_blocks;
		ret = pool->map + offset;
	}
fail:
	fio_sem_up(pool->lock);
	return ret;
}

static size_t size_to_alloc_size(size_t size)
{
	size_t alloc_size = size + sizeof(struct block_hdr);

	/*
	 * Round to int alignment, so that the postred pointer will
	 * be naturally aligned as well.
	 */
#ifdef SMALLOC_REDZONE
	alloc_size += sizeof(unsigned int);
	alloc_size = (alloc_size + int_mask) & ~int_mask;
#endif

	return alloc_size;
}

static void *smalloc_pool(struct pool *pool, size_t size)
{
	size_t alloc_size = size_to_alloc_size(size);
	void *ptr;

	ptr = __smalloc_pool(pool, alloc_size);
	if (ptr) {
		struct block_hdr *hdr = ptr;

		hdr->size = alloc_size;
		fill_redzone(hdr);

		ptr += sizeof(*hdr);
		memset(ptr, 0, size);
	}

	return ptr;
}

static void smalloc_print_bitmap(struct pool *pool)
{
	size_t nr_blocks = pool->nr_blocks;
	unsigned int *bitmap = pool->bitmap;
	unsigned int i, j;
	char *buffer;

	if (!enable_smalloc_debug)
		return;

	buffer = malloc(SMALLOC_BPI + 1);
	if (!buffer)
		return;
	buffer[SMALLOC_BPI] = '\0';

	for (i = 0; i < nr_blocks; i++) {
		unsigned int line = bitmap[i];

		/* skip completely full lines */
		if (line == -1U)
			continue;

		for (j = 0; j < SMALLOC_BPI; j++)
			if ((1 << j) & line)
				buffer[SMALLOC_BPI-1-j] = '1';
			else
				buffer[SMALLOC_BPI-1-j] = '0';

		log_err("smalloc: bitmap %5u, %s\n", i, buffer);
	}

	free(buffer);
}

void smalloc_debug(size_t size)
{
	unsigned int i;
	size_t alloc_size = size_to_alloc_size(size);
	size_t alloc_blocks;

	alloc_blocks = size_to_blocks(alloc_size);

	if (size)
		log_err("smalloc: size = %lu, alloc_size = %lu, blocks = %lu\n",
			(unsigned long) size, (unsigned long) alloc_size,
			(unsigned long) alloc_blocks);
	for (i = 0; i < nr_pools; i++) {
		log_err("smalloc: pool %u, free/total blocks %u/%u\n", i,
			(unsigned int) (mp[i].free_blocks),
			(unsigned int) (mp[i].nr_blocks*sizeof(unsigned int)*8));
		if (size && mp[i].free_blocks >= alloc_blocks) {
			void *ptr = smalloc_pool(&mp[i], size);
			if (ptr) {
				sfree(ptr);
				last_pool = i;
				log_err("smalloc: smalloc_pool %u succeeded\n", i);
			} else {
				log_err("smalloc: smalloc_pool %u failed\n", i);
				log_err("smalloc: next_non_full=%u, nr_blocks=%u\n",
					(unsigned int) mp[i].next_non_full, (unsigned int) mp[i].nr_blocks);
				smalloc_print_bitmap(&mp[i]);
			}
		}
	}
}

void *smalloc(size_t size)
{
	unsigned int i, end_pool;

	if (size != (unsigned int) size)
		return NULL;

	i = last_pool;
	end_pool = nr_pools;

	do {
		for (; i < end_pool; i++) {
			void *ptr = smalloc_pool(&mp[i], size);

			if (ptr) {
				last_pool = i;
				return ptr;
			}
		}
		if (last_pool) {
			end_pool = last_pool;
			last_pool = i = 0;
			continue;
		}

		break;
	} while (1);

	log_err("smalloc: OOM. Consider using --alloc-size to increase the "
		"shared memory available.\n");
	smalloc_debug(size);
	return NULL;
}

void *scalloc(size_t nmemb, size_t size)
{
	return smalloc(nmemb * size);
}

char *smalloc_strdup(const char *str)
{
	char *ptr = NULL;

	ptr = smalloc(strlen(str) + 1);
	if (ptr)
		strcpy(ptr, str);
	return ptr;
}